unist-util-is

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[unist][unist] utility to check if a node passes a test.

Install

[npm][]:

sh
npm install unist-util-is

Use

js
var is = require('unist-util-is')

var node = {type: 'strong'}
var parent = {type: 'paragraph', children: [node]}

function test(node, n) {
  return n === 5
}

is() // => false
is({children: []}) // => false
is(node) // => true
is(node, 'strong') // => true
is(node, 'emphasis') // => false

is(node, node) // => true
is(parent, {type: 'paragraph'}) // => true
is(parent, {type: 'strong'}) // => false

is(node, test) // => false
is(node, test, 4, parent) // => false
is(node, test, 5, parent) // => true

API

is(node[, test[, index, parent[, context]]])

Parameters

• node ([Node][node]) — Node to check.
• test ([Function][test], string, Object, or Array.<Test>, optional) — When nullish, checks if node is a [Node][node]. When string, works like passing node => node.type === test. When array, checks if any one of the subtests pass. When object, checks that all keys in test are in node, and that they have strictly equal values
• index (number, optional) — [Index][] of node in parent
• parent ([Node][node], optional) — [Parent][] of node
• context (*, optional) — Context object to invoke test with

Returns

boolean — Whether test passed *and* node is a [Node][node] (object with type set to a non-empty string).

function test(node[, index, parent])

Parameters

• node ([Node][node]) — Node to check
• index (number?) — [Index][] of node in parent
• parent ([Node?][node]) — [Parent][] of node

Context

* — The to is given context.

Returns

boolean? — Whether node matches.

is.convert(test)

Create a test function from test, that can later be called with a node, index, and parent. Useful if you’re going to test many nodes, for example when creating a utility where something else passes an is-compatible test.

The created function is slightly faster because it expects valid input only. Therefore, passing invalid input, yields unexpected results.

Can also be accessed with require('unist-util-is/convert').

For example:

js
var u = require('unist-builder')
var convert = require('unist-util-is/convert')

var test = convert('leaf')

var tree = u('tree', [
  u('node', [u('leaf', '1')]),
  u('leaf', '2'),
  u('node', [u('leaf', '3'), u('leaf', '4')]),
  u('leaf', '5')
])

var leafs = tree.children.filter((child, index) => test(child, index, tree))

console.log(leafs)

Yields:

js
[{type: 'leaf', value: '2'}, {type: 'leaf', value: '5'}]

Related

• [unist-util-find-after](https://github.com/syntax-tree/unist-util-find-after) — Find a node after another node
• [unist-util-find-before](https://github.com/syntax-tree/unist-util-find-before) — Find a node before another node
• [unist-util-find-all-after](https://github.com/syntax-tree/unist-util-find-all-after) — Find all nodes after another node
• [unist-util-find-all-before](https://github.com/syntax-tree/unist-util-find-all-before) — Find all nodes before another node
• [unist-util-find-all-between](https://github.com/mrzmmr/unist-util-find-all-between) — Find all nodes between two nodes
• [unist-util-filter](https://github.com/syntax-tree/unist-util-filter) — Create a new tree with nodes that pass a check
• [unist-util-remove](https://github.com/syntax-tree/unist-util-remove) — Remove nodes from tree

Contribute

See [contributing.md in syntax-tree/.github][contributing] for ways to get started. See [support.md][support] for ways to get help.

This project has a [code of conduct][coc]. By interacting with this repository, organization, or community you agree to abide by its terms.

License

[MIT][license] © [Titus Wormer][author]

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[license]: license

[author]: https://wooorm.com

[contributing]: https://github.com/syntax-tree/.github/blob/HEAD/contributing.md

[support]: https://github.com/syntax-tree/.github/blob/HEAD/support.md

[coc]: https://github.com/syntax-tree/.github/blob/HEAD/code-of-conduct.md

[unist]: https://github.com/syntax-tree/unist

[node]: https://github.com/syntax-tree/unist#node

[parent]: https://github.com/syntax-tree/unist#parent-1

[index]: https://github.com/syntax-tree/unist#index

[test]: #function-testnode-index-parent